Abstract: A field experiment was carried out to evaluate the changes of spatial distribution of Cleistogenes squarrosa population on Stipagrandis steppe under different utilization regimes (exclosure, mowing, and grazing) in Maodeng ranch, Xilingol, Inner Mongolia. With geostatistics, the semivariance function, fractal dimension and Kriging interpolation method, we analyzed the effects of small-scale spatial heterogeneity of C. squarrosa population in exclosure, grazing, and mowing treatments. The results showed that population density of C. squarrosa followed the order: grazing (28.63 plants·m^-2) > exclosure (13.60 plants·m^-2) > mowing (3.85 plants·m^-2) (P<0.05). Grazing increased while mowing reduced population density of C. squarrosa (both P<0.05). Population densities of C. squarrosa under the treatments of exclosure, grazing and mowing were consistent with exponential model, spherical model and spherical model, respectively. According to the results of spatial distribution pattern analysis, the structural ratio ofC. squarrosa population under mowing, grazing and exclosure was 91.9%, 75.3%, and 71.1%, respectively. The spatial autocorrelations of grazing and mowing treatments were higher mainly due to structural factors, while that of the exclosure treatment was moderate and affected by random factors. Combined with the fractal dimension and 2D and 3D views, the spatial structure of the three plots was good with simple spatial distribution, indicating that reasonable grazing and mowing did not impact the distribution of C. squarrosa population. Compared to the exclosure treatment, grazing increased and mowing reduced the spatial heterogeneity of C. squarrosa population.

Key words: intercropping, wheat variety, faba bean fusarium wilt, functional diversity of soil microbial community, root exudates.